Polymerase chain reaction (PCR) technology is only one of several techniques that permit nucleic acid material, such as DNA, often extracted from as little as a single cell, to be amplified to hundreds of millions of copies. This is important since prior to PCR technology it was virtually impossible to detect a single DNA strand. However, when a single DNA strand, such as the DNA of the human immunodeficiency virus (HIV, otherwise known to cause AIDS), is added to amplifying reagents that will amplify the DNA of choice, hundreds of millions of copies of that DNA can be obtained in a relatively short time. Technology further allows for the detection of the amplified nucleic acid material (DNA for example), using probes that hybridize to the amplified material of choice, such probes in turn either being immobilized or immobilizable to a solid support, such as a filter membrane, and/or being labeled for detection using enzymes or other moieties.
Conventionally, this has been done by amplifying the nucleic acid material in a stoppered plastic container until the desired number of copies have been formed. Thereafter, the container is reopened, such as by unstoppering, and either the amplified copies are withdrawn and transferred to detection apparatus, or detecting reagents can be added to the container used for the amplification, so that detection is done in the same container.
It has been discovered that such a technique is unsatisfactory for convenient and widespread use of, e.g., PCR technology, because aerosols are produced in the act of unstoppering and/or transfer of fluids. Such aerosols contain a few of the amplified nucleic acid material, e.g., DNA. The aerosols then proceed to disperse within the environment. Normally, such few molecules in the environment are not of great concern. However, only one DNA molecule is needed to ruin by contamination other amplifying containers yet to be used for detection. That is, if the errant DNA molecule floats into or is carried, inadvertently, by an operator to another amplifying container yet to be used, that one molecule is all that is needed to provide the DNA needed for the next amplification. Needless to say, if the point of the next test is to see if a particular DNA is present (e.g., for HIV), and it is detected only because of the errant DNA and not that of the patient, the test is ruined. Thus, the very power of DNA amplification becomes the source of potential ruin of the tests. As a matter of fact, an entire lab has been proven to be contaminated by the unstoppering of just a few containers in which the sample has already been amplified. Although such a problem might be avoidable by using highly skilled and trained personnel who painstakingly minimize the aerosols produced, the need for such labor makes the technology impractical for general use.
Thus, it has been a problem prior to this invention to provide apparatus and a method for amplifying and detecting nucleic acid material, without contaminating the surrounding environment.
Yet another problem has been, prior to this invention, to automate the detection steps, that is, minimize the need for operator intervention. The need to transfer amplified nucleic acid material or to add detection reagents makes such automation difficult.